The overall objective of the program is to develop, optimize and validate a low-cost, high throughput vertical cavity electropolishing process for eco-friendly Bulk Processing of single- and nine-cell SRF cavities at the alpha/beta scale. To achieve this objective Faraday, along with subcontractor Cornell University are focusing on: 1) Designing and building alpha-scale Bipolar EP Cell based on vertical cavity orientation without rotation for single and multi-cell cavity processing, 2) Optimizing the Bipolar EP waveform parameters and cathode geometry to improve electropolishing performance and test in single-cell cavities, and 3) Appling the optimized Bipolar EP process to multi-cell cavities and determine performance.
During this talk we will specifically discuss recent results from our button cell cavity study studies. The button cell cavity, as shown in Figure 2, was designed and built by Cornell for their own cavity finishing process optimization using the conventional sulfuric acid HF approach. This tool enables rapid analysis of the effect of the electrofinishing applied parameter on the finish produced as a function of anode to cathode gap and active area ratio. Our recent studies that demonstrate an effect on the position of the button, orientation, gravity, electrofinishing conditions, and flow rate will specifically be discussed. Figure 2, shows the difference in removal rate and material removal ratio from the beam tube to the iris, as a function of half-cell orientation. Greater uniformity is demonstrated using the P/PR Electropolishing process as compared to the conventional H2SO4/HF process.